Predicting Climate Change in the Pacific Region – Are climate models working?

Small islands in the Pacific and East Timor are facing serious challenges from future climate change, in fact the Intergovernmental Panel on Climate Change identified these small island states as being the most vulnerable countries of the world to the adverse effects of climate change (PCCS 2013) (figure 1). Climate change will impact on a range of sectors in the Pacific region including fisheries, agriculture and tourism. While there is no shortage of awareness around the issue, the understanding and ability for communities to respond and adapt to this change is currently limited. To better understand the effects and assist with adaption planning, a three-year program, the Pacific-Australia Climate Change Science and Adaption Planning (PACCSAP), was implemented in 2009 (Department of the Environment 2014).

Pacific Islands picture

Figure 1: The Pacific Islands identified as some of the most vulnerable and part of the 3-year PACCSAP program (Source: http://www.bom.gov.au/climate/pacific)

Dr Jaclyn Brown, an ocean and climate research scientist with the Centre for Australian Weather and Climate Research at the CSIRO specialises in all things related to the Tropical Pacific Ocean and is presently part of the PACCSAP program. She is working to improve the understanding of climate change and its long-term impacts for the Pacific Islands.  Dr Brown spoke at the Climate Change Research Centre, University of New South Wales (UNSW) in May. Dr Brown explained that one of the key issues in predicting what will take place in the Pacific is that we do not have accurate estimations or predictions due to short fallings of current climate models. Traditional models provide reasonable estimates, however, Brown believes that we need much more than this if we are to provide meaningful information to this region.

p_2_Pacific-Map

Figure 2: Location of the Western Pacific Warm Pool – a key driver of ENSO (Source: http://www.bom.gov.au/climate/enso)

The key area to understand when predicting future climate in the region is the Western Pacific Warm Pool edge. Brown explained that this is important, as it is the engine of the climate system and key in the El Nino Southern Oscillation (ENSO). The equatorial Pacific is characterised by warm, fresh water in the west, and cooler, saltier water in the central and eastern part of the basin. The area between the two water masses is referred to as the edge of the Western Pacific Warm Pool (figure 2). The location of this pool edge and its movement from east to west is what drives ENSO and the fundamental changes to global climates on a decadal scale (Brown et al. 2013). To understand how well a model can predict future change, then we must understand how these models behave with historical climate data (Grouse et al. 2013).  The most up to date models used have been developed as part of the Coupled Model Intercomparison Project (CMIP), a global project that has been working to provide a framework for climate models since 2008. The project is currently in its fifth phase and so the current models are aptly named CMIP5 (CMIP 2013).

Without going into the mechanics of climate modelling, a process that would make most of our heads spin, there are some underlying factors that drive these models. Many scientists have used the 28-degree isotherm (line of equal temperature) to define the edge of the warm pool. Given the complexities of our ocean basins, however, there are a range of other factors which could also be used to define this warm pool edge including salinity gradients, convergence of ocean currents and barrier layers to name a few. The problem faced by modellers is that there is not one sole factor that appears to be able to detect the edge of the warm pool and this presents some issues when we are trying to use these models to predict what will happen in the future. So do the most recent CMIP5 models accurately simulate the western tropical Pacific? Grouse et al. (2013) and Brown et al. (2013) suggest that while there are certainly improvements there are still a number of limitations and bias in these models. Brown explained that while these recent models provide greater resolution they report between 1 – 3 degree increase in temperature. While the 2 degrees difference in estimates does not seem like a lot Brown suggests that this difference in predictions does matter, especially for the effects of ENSO and therefore the future of the Pacific islands. The benefits will be remarkable if this fine level of resolution can be achieved in climate models.

While models continue to improve, further research and improvements must be made to understand the Dynamic Warm Pool edge and how this will move in the future if we are to accurately predict changes in this region. Updated models need to combine the complexities of the system if accurate information is to be provided.  It is exciting work, which will allow us to make accurate predictions for the Pacific region and help us understand what measures need to be taken to ensure that this region can adapt to a changing climate.

References

Brown J.N, Langlais C. & Maes C. (2013) Zonal structure and variability of the Western Pacific dynamic pool edge in CMIP5, Climate Dynamics, 1-16

CMIP5 Coupled Model Intercomparison Project (2013). CMIP5 – Coupled Model Intercomparison Project Phase 5 – Overview. Accessed 15 May 2014. http://cmip-pcmdi.llnl.gov/

Department of Environment (2014) Pacific-Australia Climate Change Science and Adaption Planning Program. Accessed 27 April 2014. http://www.climatechange.gov.au/climate-change/grants/pacific-australia-climate-change-science-and-adaptation-planning-program

Grose M. R., Brown J. N., Narsey S., Brown J. R., Murphy B. F., Langlais C., Gupta A.S., Moise A.F & Irving D. B. (2014). Assessment of the CMIP5 global climate model simulations of the western tropical Pacific climate system and comparison to CMIP3. International Journal of Climatology.

Pacific Climate Change Science (2013) Future climate of the Pacific. Accessed 26 April 2014. http://www.pacificclimatechangescience.org/research-activities/future-climate-of-the-pacific

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About loutosetto

A research masters student currently studying at Macquarie University. My interests are in coastal marine ecosystems. I like the interaction between the urban and the marine environments and the specialised environments that the fauna have evolved to survive in such variable environments.
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